Process and device for measuring the thickness of printed products on moving supports

Abstract

The thickness of a printed product resting on a support is measured by a scanning unit which has two sensing elements which can be pressed back against the force of a spring. In a measuring zone, one sensing element is situated on the support and the other sensing element is situated on the printed product. By means of two laser sensors, the length of the distance between the one laser sensor and a measuring face of the first sensing element is measured and the length of the distance between the other laser sensor and a measuring face of the second sensing element is measured. From the difference between the lengths of these two distances, the thickness of the printed product can be determined. By a comparison of this thickness actual value with a prescribed thickness set value, it can then be established whether the product measured is complete or whether pages, parts, or supplements are missing or whether the product has too many pages, parts, or supplements.

That which is claimed is: 
     
       1. A process for measuring the thickness of printed products in a production line comprising the steps of: supporting a printed product upon a support while advancing the support past a measuring station;   providing a first fixed sensor and using the first sensor to detect a first distance between said first sensor and the support as the support advances past the measuring station;   providing a second fixed sensor and using the second sensor to detect a second distance between said second sensor and an upper side of the supported printed product as the printed product advances past the measuring station, said upper side facing away from said support;   calculating the difference between said first and second distances to determine the thickness of said printed product;   providing a first sensing element associated with said first sensor and having a first measuring face;   providing a second sensing element associated with said second sensor and having a second measuring face;   resting said first sensing element on the support and resting said second sensing element on top of the printed product as the support and printed product advance past the measuring station;   advancing said first and second sensing elements with the support and printed product upon which the first and second sensing elements rest; and wherein the step of using the first sensor to detect a first distance includes measuring the distance between said first measuring face and said first sensor, and wherein the step of using the second sensor to detect a second distance includes measuring the distance between said second measuring face and said second sensor.     
     
     
       2. A process according to claim 1, further including the steps of: establishing a predetermined limit value for the thickness of the printed products;   comparing the determined thickness of the printed products which advance past the measuring station with the predetermined limit value; and   generating an error signal if the determined thickness of the printed product exceeds the predetermined limit value.   
     
     
       3. A device for measuring the thickness of printed products comprising: means including a plurality of supports for moving said printed products past a measuring station, with the printed products being individually supported upon respective ones of the supports;   a first and a second fixed sensor mounted at said measuring station;   said first sensor being positioned to detect a first length characteristic of the distance between said first sensor and each support as each support moves past said measuring station, and which serves as a reference point;   said second sensor being positioned to detect a second length characteristic of the distance between said second sensor and an upper side of each printed product as each printed product moves past said measuring station, said upper side being the side facing away from its associated support;   an evaluation unit which evaluates said first and second length characteristics supplied from said first and second sensors and determines a difference between said length characteristics for each printed product which difference corresponds to the thickness of the printed product;   at least one scanning unit comprising a first and second sensing element, said first sensing element being associated with said first sensor and said second sensing element being associated with said second sensor;   means mounting said one scanning unit so as to move along with at least one of said supports past said measuring station, and such that said first sensing element contacts said at least one support during the measuring of said printed products and said second sensing element contacts the upper side of said printed products; and   said first and second sensing elements each comprising a measuring face which faces respective ones of said first and second sensors as said one scanning unit moves past said measuring station, wherein the distances between said measuring faces and respective associated sensors are measured to calculate the thickness of the printed products.   
     
     
       4. A device for measuring the thickness of printed products according to claim 3, wherein each of said supports is saddle-shaped and moves along a closed path of travel and extends transversely to the direction of support movement; and wherein said measuring faces of said sensing elements run substantially parallel with the path of movement of said supports as said supports move past the measuring station.   
     
     
       5. A device for measuring the thickness of printed products according to claim 4, wherein: said saddle-shaped supports are mounted for rotation about a common axis and said supports include supporting ends which define a circular path of movement; and   said means mounting said one scanning unit comprises means mounting said sensing elements so that said sensing elements are radially aligned with said at least one support as said sensing elements move past the measuring station, and said measuring faces are arched so as to be coaxially arranged to the circular path of movement of the supporting end of said at least one support as said sensing elements move past the measuring station.   
     
     
       6. A device for measuring the thickness of printed products according to claim 3, wherein each of said supports is saddle-shaped and moves along a closed path of travel and extends transversely to the direction of support movement; wherein said measuring faces of said sensing elements run substantially parallel with the path of movement of said at least one support as said sensing elements move past the measuring station; and   said sensing elements each include a supporting face which has a substantially V-shaped configuration and which contacts said at least one support or printed product while the product thickness is being measured.   
     
     
       7. A device for measuring the thickness of printed products according to claim 6, wherein said second sensing element which comes into contact with the printed products includes a recess at the bottom of a V-shaped groove defined by said supporting face, which recess is adapted to receive a fold of said printed products while the product thickness is being measured. 
     
     
       8. A device for measuring the thickness of printed products according to claim 3, further comprising a support member and a spring element for resiliently mounting each of said sensing elements in said support member. 
     
     
       9. A device for measuring the thickness of printed products according to claim 8, wherein said second sensing element resting on said product is coupled with said first sensing element for joint movement; and said second sensing element is displaceable relative to said first sensing element when said second sensing element is forced back in said support member against the action of said spring element.   
     
     
       10. A device for measuring the thickness of printed products according to claim 3, further comprising: a plurality of said scanning units which are mounted to move along a closed path; and   said scanning units each comprising one of said first sensing elements and one of said second sensing elements wherein said scanning units run synchronously with said printed products through said measuring station.   
     
     
       11. A device for measuring the thickness of printed products according to claim 10, wherein said supports are moved along a closed path of movement and arranged one behind the other and extend transversely to the direction of support movement; and wherein said plurality of scanning units are provided in a number which is an integral fraction of the number of said supports.   
     
     
       12. A device for measuring the thickness of printed products according to claim 3, wherein said evaluation unit compares a value based upon the measured thickness of the printed products with a standard set value and calculates the difference between these values and compares it to a predetermined acceptable deviation to generate a code signal in case said difference between the values exceeds said deviation. 
     
     
       13. A device for measuring the thickness of printed products according to claim 3 wherein said first and second sensors are each laser sensors. 
     
     
       14. A process for measuring the thickness of printed products in a production line comprising the steps of: supporting a printed product upon a support while advancing the support past a measuring station;   providing a first fixed laser sensor and a first sensing element associated with the support and using the first laser sensor and the first sensing element to detect a first distance between said first laser sensor and the support as the support advances past the measuring station;   providing a second fixed laser sensor and a second sensing element associated with an upper side of the supported printed product, and using the second laser sensor and the second sensing element to detect a second distance between said second laser sensor and an upper side of the supported printed product as the printed product advances past the measuring station, said upper side facing away from said support;   advancing said first and second sensing elements in the support advancing direction when detecting said first and second distances, and   calculating the difference between said first and second distances to determine the thickness of said printed product.   
     
     
       15. A process according to claim 14, further including the steps of: establishing a predetermined limit value for the thickness of the printed products;   comparing the determined thickness of the printed products which advance past the measuring station with the predetermined limit value; and   generating an error signal if the determined thickness of the printed product exceeds the predetermined limit value.   
     
     
       16. A device for measuring the thickness of printed products comprising: means including a plurality of supports for conveying said printed products past a measuring station, with the printed products being individually supported upon respective ones of the supports;   a first and a second fixed laser sensor mounted at said measuring station;   at least one scanning unit movable in the product conveying direction during a printed product thickness detecting operation and comprising a first and a second sensing element, said first sensing element being associated with said first sensor and said second sensing element being associated with said second sensor,   said first laser sensor and said first sensing element being positioned to detect a first length characteristic of the distance between said first laser sensor and each support as each support moves past said measuring station, said first laser sensor producing a first signal representative of said first length and which serves as a reference point;   said second laser sensor and said second sensing element being positioned to detect a second length characteristic of the distance between said second laser sensor and an upper side of each printed product as each printed product moves past said measuring station, said upper side being the side facing away from its associated support; said second laser sensor producing a second signal representative of said second length; and   an evaluation unit which evaluates said first and second signals supplied from said first and second laser sensors and determines from these signals a difference between said first and second lengths for each printed product which difference corresponds to the thickness of the printed product.   
     
     
       17. A device for measuring the thickness of printed products according to claim 16, wherein said at least one scanning unit comprises a plurality of said scanning units mounted for rotation about a fixed first axis so that each of the scanning units moves past the measuring station in radial alignment with one of said supports,   said first sensing element of each scanning unit including a first measuring face and a first supporting face, with the first measuring face being aligned with said first laser sensor and with the first supporting face contacting the associated support as the first sensing element moves past the measuring station, and   said second sensing element of each scanning unit including a second measuring face and a second supporting face, with the second measuring face being aligned with said second laser sensor and with the second supporting face contacting the printed product on the associated support as the second sensing element moves past the measuring station.   
     
     
       18. A device for measuring the thickness of printed products according to claim 17 wherein said plurality of supports are mounted for rotation about a second fixed axis which is parallel to and spaced from said fixed first axis.